1. Field of the Invention
The invention is directed to a modular machining center comprising various work modules, each of which comprises tools which are positively controlled with respect to time, e.g. punching/bending tools, front-feed devices, welding stations, assembly and the like.
2. Description of the Related Art
Such machining centers are known and are distinguished particularly by the fact that the work modules can be used for multiple functions resulting in extremely economical use. Conventionally, the core element of such machining centers is a punching/bending tool unit which comprises a main drive in a base. The main drive drives a central drive gear which is supported above it in a separate housing; the central drive gear drives a plurality of work units such as bending carriages or slides, cutting punches, welding electrodes etc. in a predetermined sequence with respect to time. The drive of other adjoining work units, e.g. (semi-finished product) front-feed devices or presses, is derived from this main drive, for which purpose more or less bulky drive means are generally required in the area of the interfaces between the work units. Therefore, the attempt was made to accommodate a portion of these drive means in an enlarged base; but this severely limited the possibilities for a modular combination of a plurality of work modules.
Such conventional concepts are known e.g. from U.S. Pat. No. 44 57 160 and from EP 0 119 599 B1 and DE-AS 27 37 442. In all of the known cases, the possibilities for converting the machining center are limited to the exchange of a housing resting on a relatively broad base; relatively costly manipulating devices are required for this purpose which, moreover, require time-consuming manipulation. For example, the conversion of the machining center according to EP 0 119 599 requires a separate transport car having a highly loadable swivel axle, wherein separate means are required for bringing the unit housing to be exchanged into a plane in which it can be coupled to the base. In the machining center according to DE-AS 27 37 442, the exchangeability of the bending units likewise requires an elongated substructure, wherein the plug-in shaft connection more or less severely limits the possibilities of exchanging the work units. An uncoupling of the modules is possible only by means of lateral movement.
Moreover, it has been shown that the main drive frequently reaches the limits of its capacity when all possible coupling points of the module are used up.
As a result of these conventional difficulties in the modular construction and conversion of machining centers, the central drive rim of a classical punch/bending tool unit has begun to be replaced (see DE-PS 32 34 981) by horizontal drive shafts and the work modules to be connected linearly one after the other, wherein a separate main drive block is provided, from which all drive movements are derived. However, the substantial advantage of the central drive rim, which consists in the freely movable arrangement of the bending tool units accompanied by a uniform distribution of power, is forfeited with this concept. Another disadvantage of this concept consists in that conversion steps take up a relatively great amount of time and a relatively great amount of construction space is required for the main drive block, especially since the latter generally has large dimensions so that as many modules as possible can be connected in tandem.